Penicillin derivatives

ABSTRACT

This invention provides a penicillin derivative of the formula and a salt thereof ##STR1## wherein X represents chlorine atom or bromine atom and R represents hydrogen atom or penicillin carboxy-protecting radical, and a process for preparing the derivative of the formula (I) and a salt thereof by reacting a compound of the formula ##STR2## wherein R is as defined above with a chlorinating reagent or brominating reagent and, when required, forming a salt thereof.

This invention relates to penicillin derivatives usable as a startingmaterial for preparing derivatives of 2β-(substitutedmethyl)-2α-methylpenam-3α-carboxylic acid having β-lactamase inhibitoryproperties and to a process for preparing the same.

Of the commercially available antibiotics, β-lactam type antibioticshaving a β-lactam ring, namely penicillins and cephalosporins, are bestknown and frequently used. Although widely used as usefulchemotherapeutic drugs, the β-lactam type antibiotics can not achievesatisfactory effects against some types of microorganisms because ofresistance of the microorganism to the β-lactam type antibiotics. Theresistance thereof are usually attributable to β-lactamase produced bythe microorganism. The β-lactamase is an enzyme which acts to cleave theβ-lactam ring of the β-lactam type antibiotic, thereby causing theantibiotic to lose its antimicrobial activity. For this reason, theaction of β-lactamase must be eliminated or inhibited so as to enablethe β-lactam type antibiotic to produce satisfactory effects. Theelimination or inhibition of the β-lactamase activity can be achieved byβ-lactamase inhibitors, which are used conjointly with the β-lactam typeantibiotic to increase the antimicrobial activity of the antibiotic. Inrecent years, research on β-lactamase inhibitors has been extensivelyconducted. The β-lactamase inhibitors under investigation includederivatives of 2β-(substituted methyl)-2α-methylpenam-3α-carboxylic acid1,1-dioxide.

An example of the derivatives is described in Japanese Unexamined PatentPublication No. 104886/1981 which discloses2β-chloromethyl-2α-methylpenam-3α-carboxylic acid 1,1-dioxide havingβ-lactamase inhibiting activity and represented by the formula ##STR3##

The following two compounds of the formulae (III) and (IV) also have ahigh β-lactamase inhibitory action. ##STR4## wherein R₁ and R₂ representlower alkyl radical.

We found that the compounds of the formulae (III) and (IV) can bereadily prepared by using as a starting material a penicillin derivativeof the following formula or a salt thereof ##STR5## wherein X representschlorine atom or bromine atom, and R represents hydrogen atom orpenicillin carboxy-protecting radical. We also found that the compoundof the formula (I) can be used as an excellent starting material forsynthesizing the compound of the formula (II). The present invention wasaccomplished based on these novel findings.

The penicillin derivatives of the present invention are represented bythe formula ##STR6## wherein X and R are as defined above.

Illustrative salts of the derivatives having the formula (I) which areprepared according to the present invention include salts of alkalimetals such as sodium, potassium and lithium; salts of alkaline earthmetals such as calcium and magnesium; salts of organic amines such ascyclohexylamine, trimethylamine and diethanolamine; salts of basic aminoacids such as alginine and lysine; ammonium salts; etc.

Examples of the penicillin carboxy-protecting radicals represented by Rin the formula (I) include known radicals. Representative radicals areset forth in Japanese Unexamined Publication No. 81380/1974 and H. E.Flynn, "Cephalosporin And Penicillins Chemistry And Biology" (1972,Academic Press). Specific examples of the penicillin carboxy-protectingradicals are methyl, ethyl, propyl, tert-butyl, pentyl, hexyl and likelower alkyl groups; iodomethyl, 2,2-dibromoethyl, 2,2,2-trichloroethyland like halogenated lower alkyl groups substituted with 1 to 3 halogenatoms such as Cl, Br or I; benzyl, p-methoxybenzyl, o-nitrobenzyl,p-nitrobenzyl, diphenylmethyl and like methyl group substituted with 1to 3 phenyl groups which may be unsubstituted or may be substituted withmethoxy or nitro on the phenyl ring; methoxymethyl, ethoxymethyl,n-propyloxymethyl, iso-propyloxymethyl, n-butoxymethyl, iso-butoxymethyland like lower alkoxymethyl groups; acetoxymethyl, propionyloxymethyl,n-butyryloxymethyl, iso-butyryloxymethyl, pivalyloxymethyl,1-acetoxyethyl, 1-pivalyloxyethyl, 1-pivalyloxypropyl,1-propionyloxybutyl and like lower alkyl-carbonyloxy-lower alkyl;cyclopentylcarbonyloxymethyl, cyclohexylcarbonyloxymethyl and like (C₅-C₇ cycloalkyl)-carbonyloxy-lower alkyl groups; benzylcarbonyloxymethyland like benzylcarbonyloxy-lower alkyl groups; benzoyloxymethyl,benzoyloxyethyl and like benzoyloxy-lower alkyl groups, etc. The term"lower" used in conjunction with "alkyl" or "alkoxy" is intended toindicate that each alkyl or alkoxy portion therein can contain 1 to 6carbon atoms. The alkyl or alkoxy groupings can be straight- orbranched-chain groups. Other examples of the penicillincarboxy-protecting radicals include phthalidyl, tetrahydropyranyl,5-oxo-2-tetrahydrofuranyl, dimethylaminoethyl, dimethylchlorosilyl,trichlorosilyl, etc.

The compounds of the present invention are

(1) 2β-chloromethyl-2α-methylpenam-3α-carboxylic acid,

(2) 2β-bromomethyl-2α-methylpenam-3α-carboxylic acid and the foregoingsalts thereof and the aforesaid esters thereof.

The penicillin derivatives of the present invention having the formula(I) are prepared by reacting a compound represented by the formula##STR7## wherein R is as defined above with a chlorinating reagent orbrominating reagent.

The compounds of the formula (V) are known and are prepared by theprocess disclosed in Japanese Unexamined Patent Publication No.130981/1980.

Typical chlorinating reagents are hydrogen chloride, cupric chloride,mercuric chloride, etc. Typical brominating reagents are hydrogenbromide, cupric bromide, mercuric bromide, etc. The reaction accordingto this invention is usually conducted in a solvent. Usable as thesolvent is any of solvents which do not affect the reaction, such aschloroform, methylene chloride, carbon tetrachloride and likehalogenated hydrocarbons, acetone, acetonitrile, methanol, ethanol,acetic acid, etc.

The reaction temperature is suitably determined according to the type ofthe reagent to be used, and generally ranges from about -40° C. to roomtemperature. For example, when cupric chloride or cupric bromide isused, the reaction temperature ranges from -20° C. to room temperature.

In the reaction between the compound of the formula (V) and thechlorinating reagent or the brominating reagent, at least one mole ofthe reagent is used per mole of the compound of the formula (V), andpreferably they are employed in equimolecular amounts.

The compounds of the formula (I) wherein R represents a hydrogen atomcan alternatively be prepared by eliminating the carboxy-protectinggroup of the esters of the formula (I) wherein R represents thecarboxy-protecting radical. The method of eliminating thecarboxy-protecting radical depends upon the kind of carboxy-protectingradical. Generally, however, such elimination can be achieved by eitherreducing the ester or treating the ester with an acid.

The reduction can be conducted by treating the ester of the formula (I)with a mixture of (a) zinc, zinc-amalgam or like metal and/or chromiumchloride, chromium acetate or like chromium salt and (b) formic acid,acetic acid or like acid. Alternatively, the reduction can be conductedwith use of a catalyst in hydrogen atmosphere in a solvent. Examples ofthe catalysts are platinum, platinum oxide, palladium, palladium oxide,palladium-barium sulfate, palladium-calcium carbonate, palladium-carbon,nickel oxide, Raney-nickel, etc. The solvents are not particularlylimited so far as they do not affect the reaction, and include methanol,ethanol and like alcohols; tetrahydrofuran, dioxane and like ethers;ethyl acetate and like esters; acetic acid and like fatty acids; and amixture of these organic solvents and water.

The acids useful for eliminating the carboxy-protecting group of theester of the formula (I) are formic acid, acetic acid and like lowerfatty acids; trichloroacetic acid, trifluoroacetic acid and liketrihalogenated acetic acids; hydrochloric acid, hydrofluoric acid andlike hydrohalogenic acids; p-toluene-sulfonic acid,trifluoromethane-sulfonic acid and like organic sulfonic acids; and amixture of these. In this reaction, when the acid used is in a liquidstate and acts also as a solvent, it is not necessary to use othersolvents. However, dimethylformamide, dichloromethane, chloroform,tetrahydrofuran, acetone and like solvents which do not affect thereaction may be used.

Salts of the penicillin derivatives of the formula (I) can be preparedby reacting the free penicillin carboxylic acid with an inorganic ororganic base. Examples of the inorganic base are sodiumhydrogencarbonate, sodium carbonate, sodium hydroxide, potassiumhydrogencarbonate, potassium carbonate, potassium hydroxide, lithiumcarbonate, lithium hydroxide; calcium carbonate, calcium hydroxide,magnesium carbonate, magnesium hydroxide, etc. Examples of the organicamines are cyclohexylamine, trimethylamine, diethanolamine, basic aminoacids, ammonia, etc. Amount of the inorganic or organic base to be usedis about 0.5 to about 2 moles, per mole of the free penicillincarboxylic acid. The reaction is conducted in a solvent. Useful solventsare not particularly limited so far as they do not affect the reaction,and include methanol, ethanol and like alcohols; N,N-dimethylformamide,dimethylsulfoxide and like aprotic polar organic solvents, etc.

The salts may also be prepared by a salt exchange reaction in which thefree penicillin carboxylic acid is reacted with a salt of astraight-chain or branched-chain fatty acid in a solvent. The solventsare not particularly limited so far as they are capable of precipitatingthe resulting salt of the penicillin carboxylic acid, and include ethylacetate, butanol, etc.

Alternatively, the salts can be prepared from the ester of thepenicillin carboxylic acid. First, the carboxy-protecting radical of theester is eliminated in a solvent which contains the foregoing inorganicbase, thereby to concurrently form the salt. Useful solvents are thosewhich do not affect the reaction, and include tetrahydrofuran, dioxaneand like ethers, ethyl acetate and like acetates; and a mixture of theseand water.

The compounds thus obtained are purified by conventional methods such asrecrystallization, extraction, column chromatography, etc.

The present invention will be described below in more detail withreference to reference examples and examples. Reference examplesdescribe the process for preparing the compound of the formula (II),(III) or (IV) by using the compound of the formula (I) of the presentinvention.

REFERENCE EXAMPLE 1 Preparation of benzhydryl ester of2β-chloromethyl-2α-methylpenam-3α-carboxylic acid 1,1-dioxide

Potassium permanganate (1.2 g) was added under stirring to a solution ofbenzhydryl ester of 2β-chloromethyl-2α-methylpenam-3α-carboxylic acid(1.40 g) in a mixture of acetic acid (60 ml) and water (8 ml). Thereaction mixture was agitated at room temperature for 3 hours, and thenice and water (100 ml) were added to produce a white precipitate whichwas filtered off. The precipitate was washed with ice water, and wasdissolved in ethyl acetate. The solution was dried over magnesiumsulfate, and the solvent was removed by distillation. There was obtained1.1 g of benzhydryl ester of2β-chloromethyl-2α-methylpenam-3α-carboxylic acid, 1,1-dioxide.

Infrared absorption spectrum (nujol). ν_(max) (cm⁻¹): 1800, 1750.

Nuclear magnetic resonance spectrum (CDCl₃) δ(ppm): 1,25 (3H, s), 3.43(2H, d).

REFERENCE EXAMPLE 2 (A) Preparation of benzhydryl ester of2β-azidomethyl-2α-methylpenam-3α-carboxylic acid

An aqueous solution (25 ml) containing 2.38 g of sodium azide was addedto a solution of benzhydryl ester of2β-chloromethyl-2α-methylpenam-3α-carboxylic acid (2.44 g) indimethylformamide (100 ml). The mixture was stirred at room temperaturefor 4 hours. The reaction mixture was poured into water and theresulting mixture was extracted with ether. The ether layer was washedwith water and concentrated, giving 2.2 g of oil in 89% yield.

Infrared absorption spectrum (nujol). ν_(max) (cm⁻¹): 2120, 1812, 1765.

Nuclear magnetic resonance spectrum (CDCl₃). δ(ppm): 1.30 (3H, s), 3.25(2H, m), 3.42 (1H, d), 3.63 (1H, d), 4.75 (1H, s), 4.76 (1H, m), 7.00(1H, s), 7.40 (10H, s).

(B) Preparation of benzhydryl ester of2β-azidomethyl-2α-methylpenam-3α-carboxylic acid 1,1-dioxide

Benzhydryl ester of 2β-azidomethyl-2α-methyl-penam-3α-carboxylic acid(2.22 g) and potassium permanganate (1.9 g) were added to a mixture ofacetic acid (75 ml) and water (12 ml). The mixture was stirred at roomtemperature for 4 hours and ice water was added to produce a precipitatewhich was filtered off. The precipitate was washed with water anddissolved in ether. The solution was washed with an aqueous solution ofsodium hydrogen carbonate and concentrated. There was obtained 1.49 g ofthe contemplated product in 62.2% yield.

Infrared absorption spectrum (nujol). ν_(max) (cm⁻¹): 2120, 1812, 1765.

Nuclear magnetic resonance spectrum (CDCl₃) δ(ppm): 1.18 (3H, s), 3.50(2H, d), 3.72 (1H, d), 3.93 (1H, d), 4.60 (1H, m), 4.65 (1H, s), 7.00(1H, s), 7.36 (10H, s).

REFERENCE EXAMPLE 3 Preparation of benzhydryl ester of2β-(4,5-dimethoxycarbonyl-1,2,3-triazol-1-yl)methyl-2α-methylpenam-3α-carboxylicacid 1,1-dioxide

Benzhydryl ester of 2β-azidomethyl-2α-methylpenam 3α-carboxylic acid1,1-dioxide (0.870 g) and dimethyl acetylene-dicarboxylate (0.618 g)were refluxed with stirring in 15 ml of benzene in nitrogen atmospherefor 18 hours. The solvent was removed by distillation and the residuewas eluted by silica gel column chromatography (ethylacetate/chloroform=1:3). There was obtained 0.495 g of contemplatedproduct as light yellow crystals in 44% yield which melts at 75° to 77°C.

Infrared absorption spectrum (KBr). ν_(max) (cm⁻¹): 1800, 1735.

Nuclear magnetic resonance spectrum (CDCl₃). δ(ppm): 1.20 (3H, s), 3.48(2H, t), 3.97 (3H, s), 3.98 (3H, s), 4.59 (1H, m), 4.95 (1H, s), 5.26(2H, s), 6.97 (1H, s), 7.36 (10H, s).

EXAMPLE 1 Preparation of benzhydryl ester of2β-chloromethyl-2α-methylpenam-3α-carboxylic acid

A solution of benzhydryl2-oxo-4-(benzothiazol-2-yl)dithio-α-isopropenyl-1-azetidine acetate (2.1g) and cupric chloride (0.5 g) in methylene chloride (100 ml) wasstirred at room temperature for 5 hours. The reaction mixture wasfiltered, and the filtrate was washed with water, dried over magnesiumsulfate and concentrated to provide a yellow oil. The oil was subjectedto chromatography on a silica gel column, producing 1.4 g of benzhydrylester of 2β-chloromethyl-2α-methylpenam-3α-carboxylic acid from afraction of methylene chloride.

Infrared absorption spectrum (Nujol). ν_(max) (cm⁻¹): 1800, 1750.

Nuclear magnetic resonance spectrum (CDCl₃). δ(ppm): 1.42 (3H, s), 3.07(1H, dd), 3.58 (1H, dd), 3.63 (2H, s), 5.19 (1H, s), 5.42 (1H, dd), 7.0(1H, s), 7.4 (10H, m).

EXAMPLE 2

Following the general procedure of Example 1 and substituting thereinthe appropriate reactants affords p-nitrobenzyl ester of2β-chloromethyl-2α-methylpenam-3α-carboxylic acid.

Melting point: 103° to 104° C. (white crystals).

Infrared absorption spectrum (KBr). ν_(max) (cm⁻¹): 1780, 1750.

Nuclear magnetic resonance spectrum (CDCl₃). δ(ppm): 1.49 (3H, s), 3.14(1H, dd), 3.65 (1H, dd), 3.62 (2H, s), 5.12 (1H, s), 5.30 (2H, bd),5.3-5.5 (1H, m), 7.5-7.7 (2H, m), 8.1-8.4 (2H, m).

EXAMPLE 3 Preparation of benzyhydryl ester of2β-bromomethyl-2α-methylpenam-3α-carboxylic acid

A solution of benzhydryl2-oxo-4-(benzothiazol-2-yl)dithio-α-isopropenyl-1-azetidine acetate (2.8g) and cupric bromide (1.28 g) in methylene chloride (60 ml) at -10° C.for 4 hours. The reaction mixture was filtered, and the residue waswashed with methylene chloride. The methylene chloride solutions werecombined, and the mixture was washed with a solution of sodium hydrogencarbonate and further with water, and dried over magnesium sulfate. Theresulting solution was concentrated to provide a light yellow oil. Theoil was subjected to column chromatography, producing 2.2 g ofcontemplated product from a fraction of methylene chloride.

Infrared absorption spectrum (KBr). ν_(max) (cm⁻¹): 1780, 1730.

Nuclear magnetic resonance spectrum (CDCl₃). δ(ppm): 1.40 (3H, s),2.9-3.3 (1H, m), 3.4-3.8 (1H, m), 3.60 (2H, s), 5.25 (1H, s), 5.3-5.5(1H, m), 6.95 (1H, s), 7.1-7.8 (10H, m).

We claim:
 1. A penicillin derivative represented by the followingformula and alkali metal, alkaline earth metal, cyclohexylamine,trimethylamine, diethanolamine, alginine, lysine or ammonium saltsthereof ##STR8## wherein X represents chlorine atom or bromine atom, andR represents hydrogen atom, C₁₋₆ alkyl, C₁₋₆ alkyl substituted with 1 to3 halogen atoms, methyl group substituted with 1 to 3 phenyl groupswhich may optionally be substituted with methoxy or nitro on the phenylring, C₁₋₆ alkoxymethyl, C₁₋₆ alkylcarbonyloxy-C₁₋₆ alkyl, (C₅₋₇cycloalkyl)carbonyloxy-C₁₋₆ alkyl, benzylcarbonyloxy-C₁₋₆ alkyl,benzoyloxy-C₁₋₆ alkyl, phthalidyl, tetahydropyranyl,5-oxo-2-tetrahydrofuranyl, dimethylaminoethyl, dimethylchlorosilyl ortrichlorosilyl.
 2. A compound as defined in claim 1 wherein methyl groupsubstituted with 1 to 3 phenyl groups which may optionally besubstituted with methoxy or nitro on the phenyl ring represented by R isbenzyl, p-methoxybenzyl, p-nitrobenzyl, o-nitrobenzyl or diphenylmethyl.3. A compound as defined in claim 1 wherein X is a chlorine atom.
 4. Acompound as defined in claim 1 which is2β-chloromethyl-2α-methylpenam-3α-carboxylic acid.
 5. A compound asdefined in claim 1 which is 2β-chloromethyl-2α-methylpenam-3α-carboxylicacid p-nitrobenzyl ester.
 6. A compound as defined in claim 1 which is2β-chloromethyl-2α-methylpenam-3α-carboxylic acid diphenylmethyl ester.7. A compound as defined in claim 1 which is2β-bromomethyl-2α-methylpenam-3α-carboxylic acid.
 8. A compound asdefined in claim 1 which is 2β-bromomethyl-2α-methylpenam-3α-carboxylicacid diphenylmethyl ester.